When migrating a target database with different endianness than the source database, the appropriate methods to use are RMAN DUPLICATE and RMAN CONVERT. RMAN DUPLICATE can be used in combination with conversion operations to create a duplicate database on a remote host with different endianness, while RMAN CONVERT is used to convert data files between different formats, which is necessary when moving between platforms with different endianness.

For RMAN DUPLICATE operations, knowing the source database's listener port is essential for network connectivity, and the database unique name identifies the specific database instance for duplication. These pieces of information ensure RMAN can connect to and accurately identify the source database for cloning.

For decision support systems that require fast queries over large volumes of data, an Autonomous Data Warehouse (ADW) is the most suitable type of autonomous database. ADW is optimized for high-performance, large-scale data analytics and reporting, providing the necessary capabilities to support complex queries and data analysis tasks in decision support systems.

To connect an on-premises Oracle Database to an Autonomous Database on Oracle Cloud Infrastructure (OCI) using Oracle Data Integrator (ODI) on Marketplace, VPN Connect and FastConnect are viable options. VPN Connect allows for a secure, private connection over the internet, while FastConnect provides a dedicated, high-bandwidth connection. Both methods ensure a reliable and secure data transfer path from on-premises systems to OCI.

To extract data from Fusion SaaS applications and load it into Autonomous Data Warehouse (ADW) using Oracle Data Integrator (ODI), the essential topology elements include the Oracle (ADW) data server, File data server for handling flat files, and Object Storage to store and manage data files in the cloud. These components work together to facilitate the extraction, storage, and loading of data in an efficient and scalable manner.